The present invention relates to a control system for a throttle valve actuating device including a throttle valve of an internal combustion engine and an actuator for actuating the throttle valve.
One known throttle valve actuating device including a throttle valve of an internal combustion engine for a vehicle, a motor for actuating the throttle valve, and an intermediate lever stopper for maintaining the throttle valve at a predetermined opening is disclosed in Japanese Patent Laid-open No. Hei 9-72231, for example. According to this throttle valve actuating device, the throttle valve is maintained at the predetermined opening when the throttle valve actuating device fails to operate normally, to thereby make it possible for the vehicle to run for evacuation.
Since the energizing force of the spring applied to the throttle valve changes abruptly when the throttle valve opening is in the vicinity of the predetermined opening defined by the intermediate lever stopper, there is a problem that controllability of the throttle valve opening decreases in the vicinity of the predetermined opening. The predetermined opening changes depending on difference in characteristics of the throttle valve actuating device or aging of the throttle valve actuating device. Therefore, a method for calculating a learning value of the predetermined opening, and correcting the control command value for the motor when the throttle valve opening is in the vicinity of the learning value, is shown in the above publication.
According to the above publication, the learning value is calculated when a clutch provided between the throttle valve and the motor actuating the throttle valve is cut off. More specifically, the calculation of the learning value is executed during a period from the time the ignition switch is turned on to the time the cranking of the engine is started. Therefore, frequency of updating the learning value is very few, which results in low accuracy of the learning value.
It is therefore an object of the present invention to provide a control system for a throttle valve actuating device, which can obtain an accurate learning value of the throttle opening at which the operating characteristic changes, and maintain good controllability of the throttle valve opening in the vicinity of the learning value.
To achieve the above object, the present invention provides a control system for a throttle valve actuating device (10) including a throttle valve (3) of an internal combustion engine and actuating means (6) for actuating the throttle valve (3). The control system includes identifying means, learning value calculating means, and control means. The identifying means (22) identifies at least one model parameter (a1, a2, b1, c1) of a controlled object model which is obtained by modeling the throttle valve actuating device (10). The learning value calculating means calculates a learning value (THDEFxe2x88x92thdefadp) of a throttle valve opening (THDEF) at which an actuating characteristic of the throttle valve changes, according to the at least one model parameter. The control means controls the throttle valve actuating device (10) using the learning value (THDEFxe2x88x92thdefadp) so that an opening (TH) of the throttle valve coincides with a target opening (THR).
The throttle valve opening at which the actuating characteristic of the throttle valve changes implies not only the default opening THDEF described below, but also the predetermined opening defined by the intermediate lever stopper shown in Japanese Patent Laid-open No. Hei 9-72231.
With the above configuration, one or more model parameter of the controlled object model is identified, and the learning value of a throttle valve opening at which an actuating characteristic of the throttle valve changes is calculated according to the identified one or more model parameter. Accordingly, the learning value is calculated during execution of the throttle valve actuating control, which increases the frequency of calculation and improves accuracy of the learning value.
Preferably, the throttle valve actuating device (10) includes first energizing means (4) for energizing the throttle valve in a closing direction and second energizing means (5) for energizing the throttle valve in an opening direction, and maintains the throttle valve opening (TH) at a default opening (THDEF) by the first and second energizing means when the throttle valve is not actuated by the actuating means (6), and the learning value calculating means calculates the learning value (THDEFxe2x88x92thdefadp) of the default opening (THDEF).
With this configuration, the throttle valve is energized in the closing direction by the first energizing means and energized in the opening direction by the second energizing means. The throttle valve is maintained at the default opening when the actuating means is not actuating the throttle valve. The learning value of the default opening is calculated by the learning value calculating means. By calculating the learning value of the default opening and using the calculated learning value in the control, controllability in the vicinity of the default opening can be improved, since the actuating characteristic of the throttle valve abruptly changes in the vicinity of the default opening.
Preferably, the controlled object model is defined by one or more first model parameter (a1, a2) which is relevant to an output of the throttle valve actuating device, a second model parameter (b1) which is relevant to a control input to the throttle valve actuating device (10), and a third model parameter (c1) which is irrelevant to both of the control input and the output of the throttle valve actuating device (10).
By employing the third model parameter which is irrelevant to both of the control input and the output of the throttle valve actuating device, it is possible to reduce the modeling error (difference between the characteristics of the throttle valve actuating device and the characteristics of the controlled object model) in the vicinity of the default opening where the throttle valve actuating device has relatively strong non-linear characteristics, and to improve the accuracy of identified model parameters. Accordingly, the accuracy of the calculated learning value is improved.
Preferably, the learning value calculating means calculates the learning value (THDEFxe2x88x92thdefadp) of the throttle valve opening at which the actuating characteristic of the throttle valve changes, according to the third model parameter (c1).
With this configuration, the learning value of the throttle valve opening at which the actuating characteristic of the throttle valve changes is calculated according to the third model parameter. When a deviation amount (DTH) between the detected throttle valve opening and the throttle valve opening at which the actuating characteristic of the throttle valve changes (hereinafter referred to as xe2x80x9ccharacteristic-change openingxe2x80x9d) is used as an output of the controlled object model, the third model parameter (c1) indicates a sum of a deviation (thdefadp) of the characteristic-change opening and disturbance. Accordingly, the deviation (thdefadp) of the characteristic-change opening is calculated based on the third model parameter, and the learning value (THDEFxe2x88x92thdefadp) of the characteristic-change opening can be calculated using the deviation (thdefadp) of the characteristic-change opening. Therefore, the characteristic-change opening, i.e., the throttle valve opening at which the actuating characteristic of the throttle valve changes, can easily be calculated during execution of the actuating control of the throttle valve.
Preferably, the control means includes a sliding mode controller (21) for controlling the throttle valve actuating device (10) with the sliding mode control using the at least one model parameter (a1, a2, b1, c1) identified by the identifying means.
With this configuration, the throttle valve actuating device is controlled with the sliding mode control using one or more model parameter identified by the identifying means. Since the sliding mode control has strong robustness, good stability and controllability of the control can be maintained even in the presence of the modeling error due to a difference between the actual dead time of the throttle valve actuating device and the dead time of the controlled object model.
Preferably, the control input (Usl) from the sliding mode controller (21) to the throttle valve actuating device (10) includes an adaptive law input (Uadp).
With this configuration, better controllability is obtained even in the presence of disturbance and/or the modeling error.
The present invention further provides a control system for a throttle valve actuating device (10) including a throttle valve (3) of an internal combustion engine, actuating means (6) for actuating the throttle valve, first energizing means (4) for energizing the throttle valve in a closing direction, and second energizing means (5) for energizing the throttle valve in an opening direction. The throttle valve actuating device (10) maintains an opening (TH) of the throttle valve at a default opening (THDEF) by the first and second energizing means (4, 5) when the throttle valve is not actuated by the actuating means (6). The control system includes learning value calculating means and control means. The learning value calculating means calculates a learning value (THDEFxe2x88x92thdefadp) of the default opening when the actuating means (6) is actuating the throttle valve (3). The control means controls the throttle valve actuating device (10) using the learning value (THDEFxe2x88x92thdefadp) so that the throttle valve opening (TH) coincides with a target opening (THR).
With this configuration, the learning value of the default opening is calculated when the actuating means is actuating the throttle valve. That is, the calculation of the learning value is executed during execution of the throttle valve actuating control. Accordingly, the frequency of the learning value calculation increases so that the accuracy of the learning value is improved.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate embodiments of the present invention by way of example.